Preheat oven to 190°C. Line 2 baking trays with non-stick baking paper. Use an electric beater to beat the butter and sugar in a bowl until pale and creamy. Beat in the egg.

Step 2

Stir in the bicarbonate of soda, carrot, walnuts, cinnamon and to combine. Use a metal spoon to fold in flour and buttermilk, in alternating batches, until just smooth. The mixture should be a little stiff.

Step 3

Use a 3cm-diameter ice-cream scoop to place rounds of the mixture onto prepared trays, leaving 5cm for spreading. Use your finger to smooth mixture around the edges.

Step 4

Bake, swapping the trays halfway through cooking, for 10 minutes or until firm. Cool slightly. Place on a wire rack to cool completely. Repeat, in 2 more batches, with remaining mixture.

Step 5

To make the filling, use an electric beater to beat the cream cheese and butter in a bowl until well combined. Add the icing sugar and beat until well combined. Add the vanilla and milk and beat until mixture is pale and creamy.

Step 6

Spoon filling into a piping bag fitted with a 1cm round nozzle. Pipe a dollop over a whoopie base. Pipe half the whoopies with cream cheese frosting.

Step 7

Top with the remaining whoopies and press lightly to sandwich together.